Ozark Cavefish

Amblyopsis rosae

Description

The Ozark cavefish, Amblyopsis rosae, is a true troglobitic (cave-dwelling) fish. It is a small (2 in, or 5.1 cm), pinkish-white fish with a broad flattened head, small scales, and a projecting lower jaw. The dorsal and anal fins are located far back on the body, the caudal fin is rounded, and the pelvic fins are absent. The Ozark cavefish has only vestigal eyes. It uses sensory papillae, which occur in two or three rows on its tail fin, to "feel" its way through its environment.

The only other species in the genus Amblyopsis is the Northern cavefish (A. spelea ), found in southern Indiana and west central Kentucky. The northern and southern species are not readily distinguishable, and they differ mainly in the arrangement of their sensory organs. How they differ greatly is their degree of cave adaptation, with the Ozark cavefish being much more selective and less adaptable.

Behavior

This species is rarely seen and little is known of its life history. Free swimming fry have been observed at five to six months of age, and first reproduction begins at three to four years. Fertilization probably occurs from February to April, although only one-fifth of the females breed in a season. Females produce 20-25 eggs. The young are carried in the gill cavity until they lose their yolk sac at age four to five months.

The most available food source is bat guano, but the cavefish also feeds on copepods, cladocerans, isopods, amphipods, crayfish, crickets, larval salamanders, and young cavefish.

Habitat

The Ozark cavefish inhabits the caves that honeycomb the highly soluble Boone and Burlington limestone formations of the Ozark Mountains. Food supply in these stable, yet fragile, cave habitats is limited in diversity and quantity because of the lack of light. Larger populations of the Ozark cavefish occur in caves used by the endangered gray bat (My-otis grisescens ), where bat guano is the primary energy source. The caves occasionally flood, and the introduced waters also carry some food resources. Organic matter enters the cave entrances via wind and some food may enter through sinkholes.

Distribution

The Ozark cavefish is the only cavefish within the Springfield Plateau of southwest Missouri, northwest Arkansas, and northeast Oklahoma. Early studies of the southern cavefish (Typhlichthyssubterraneus ) often confused it with the Ozark cave-fish, and it is difficult to sort out actual sightings. Historic records place the Ozark cavefish in at least nine counties and possibly in an additional five. There are reports of the cavefish occurring in 52 caves; only 24 historic localities are confirmed, however.

As of 1990, there were 9 known populations of the Ozark cavefish in Missouri and 21 populations range-wide, including populations in at least 14 caves in six counties in Arkansas, Missouri, and Oklahoma. Discoveries of new populations in Missouri in 1989 and 1990 delighted researchers. In 1989, the presence of cavefish in Jackson Cave (Greene County) was confirmed by Dr. Steven Jones of Drury College. Another population was found in Hayes Spring Cave (Stone County). Although this population is located within the historic range of the cavefish, upon its discovery it was the only known population in Stone County. It was believed that the cavefish had been extirpated from Fantastic Caverns (Greene County), but a single cavefish was observed there in 1989, marking the first time the species had been observed in the caverns since 1981. Finally, in January 1990, cavefish were observed in a spring at the Neosho National Fish Hatchery at Neosho, Missouri.

Threats

The decline of the Ozark cavefish may be due to degradation of subsurface or groundwater. Northwest Arkansas is an area of heavy agricultural use where animal waste from poultry and swine seep into the groundwater. Sinkholes in the soluble limestone bedrock increase the possibility of direct contamination of the groundwater. Researchers from the Arkansas Department of Pollution Control and Ecology have detected nitrate and ammonia levels in regional wells that are probably toxic to the cave-fish. Industrial and residential development of Greene County, Missouri, have also caused water contamination. Toxic levels of nickel from urban wastes have been found in at least one cave system.

A low reproduction rate and a confined habitat make the Ozark cavefish vulnerable to even casual collecting. There are several documented instances of scientific collectors taking large numbers of Ozark cavefish. A scientific collection in the 1930s from one Arkansas cave may be responsible for reducing that population to a very low level. Pet stores often display blind cavefish (possibly Ozarks) for sale to aquarists. Another threat to the cavefish is disturbance caused by groups of amateur spelunkers. Protection of cavefish requires that human disturbance be kept to a minimum. The populations in caves where cavefish were once known to occur disappeared when the caves were opened to spelunkers.

Conservation and Recovery

Cave Springs Cave in Arkansas is now owned by the state, providing some protection for the largest known cavefish population. Missouri purchased Turnback Creek Cave which, although it contains only a small Ozark cavefish population, has considerable cavefish habitat and may support a rein-troduction effort. The Nature Conservancy and Arkansas Natural Heritage Commission have also purchased caves with small populations of cavefish.

Maintaining the openings into the caves so that bats can freely come and go is crucial for the continuing supply of food resources. Cave water supplies, which include drainage basins and aquifers, must be protected from surface runoff. The Recovery Plan recommends monitoring regional hydraulic patterns so that water quality can be controlled and the water table and flow can be maintained; installing gates to cave entrances to decrease disturbance by spelunkers; introduce bat populations into uncolonized recovery caves; and educate spelunkers to the harm they can inflict upon cavefish.

Contacts

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
P. O. Box 1306
Albuquerque, New Mexico 87103
http://southwest.fws.gov/

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
Federal Building
Fort Snelling, Minnesota 55111
http://midwest.fws.gov/

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
1875 Century Blvd, Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

References

Poulson, T. L. 1963. "Cave Adaptation in Amblyopsid Fishes." American Midland Naturalist 70(2):257-290.

U.S. Fish and Wildlife Service. 1986. Recovery Plan for the Ozark Cavefish, Amblyopsis rosae. U.S. Fish and Wildlife Service. Atlanta, 52 pp.

Willis, L. D., and A. V. Brown. 1985. "Distribution and Habitat Requirements of the Ozark Cavefish, Amblyopsis rosae." American Midland Naturalist 114(2):311-317.